This invention relates to a cylinder injection type two cycle engine and more particularly to an improved fuel supply system for an engine.
The advantages of providing two cycle crankcase compression internal combustion engines with direct cylinder fuel injection are well recognized. Such direct injection has the advantage of insuring more accurate control of fuel supply and a better control of the exhaust gas emission from such engines. However, in connection with the use of direct cylinder injection, the piston and specifically the lower area of the piston does not receive the normal cooling as when the engine is supplied with the fuel/air charge from the crankcase of the engine wherein the gas is compressed. Thus, piston overheating can be a problem with engines wherein only direct cylinder injection is provided.
It has, therefore, been proposed to employ an auxiliary fuel injection system that injects fuel into the crankcase chambers so as to fully cool the piston and some of the other components within the crankcase such as the connecting rod and bearing journals. However, the use of such multiple fuel injectors gives rise to a number of problems. First, it is important that the metering system be very accurate so as to insure that oversupplies of fuel are not provided and also so as to insure that the adequate cooling of the piston and other components will be achieved, particularly under high speed performance. In addition, it is necessary to provide an arrangement for separating the fuel vapors from the fuel before it is delivered to the injection nozzles. The use of multiple injectors can complicate the vapor separation with conventional engines.
It is, therefore, a principal object of this invention to provide an improved arrangement for providing a two cycle engine with direct cylinder injection but also in which some fuel is supplied to the crankcase chambers for cooling the piston, at least under high speed running.
It is a further object of this invention to provide a fuel supply system of the type as aforedescribed wherein all of the fuel is not supplied by fuel injectors.
It is yet another object of this invention to provide a fuel supply system for a two cycle crankcase compression internal combustion engine wherein a carburetor system is employed for supplying a fuel air mixture to the crankcase chambers and the engine also employs direct fuel injectors for supplying fuel directly to the combustion chambers.
As is noted above, the use of fuel injectors for an engine requires the addition of a vapor separator so as to insure that the fuel injectors will operate properly. However, it is also known that carbureted engines employ a float bowl in which the fuel is maintained at a uniform head by a float operated valve and in which a vent system is provided so that the air pressure above the fuel bowl will be the same as the static pressure existing in the induction system.
It is, therefore, a further object of this invention to provide an improved combination of carburetor and fuel injector wherein the fuel is supplied to the fuel injector from the vented fuel bowl of the carburetor so as to avoid the use of a separate vapor separator for the injector.
As noted above, in systems where there is provided a fuel supply to the engine that is direct into the combustion chambers and wherein additional fuel is also supplied to the crankcase chambers at least under high speed running for piston cooling, the fuel control system can be quite complicated.
It is, therefore, a still further object of this invention to provide a simplified fuel control system for an engine wherein fuel is supplied both directly to the combustion chambers and to the crankcase chambers for at least piston cooling.